Re: [Intel-gfx] BUG: sleeping function called from invalid context on 3.10.10-rt7

[Mario Kleiner <mario.kleiner.de@gmail.com>]

On 25.09.13 16:13, Steven Rostedt wrote:
> On Wed, 25 Sep 2013 06:32:10 +0200
> Mario Kleiner <mario.kleiner@tuebingen.mpg.de> wrote:
>
>
>> But given the new situation, your proposal is great! If we push the
>> clock readouts into the get_scanoutpos routine, we can make this robust
>> without causing grief for the rt people and without the need for a new
>> separate lock for display regs in intel-kms.
>>
>> E.g., for intel-kms:
>>
>> i915_get_crtc_scanoutpos(..., ktime_t *stime, ktime_t *etime)
>> {
>>     ...
>>     spin_lock_irqsave(...uncore.lock);
>>     preempt_disable();
>>     *stime = ktime_get();
>>     position = __raw_i915_read32(dev_priv, PIPEDSL(pipe));
>>     *etime = ktime_get();
>>     preempt_enable();
>>     spin_unlock_irqrestore(...uncore.lock)
>>     ...
>> }
>>
>> With your patchset to reduce the amount of register reads needed in that
>> function, and given that forcewake handling isn't needed for these
>> registers, this should make it robust again and wouldn't need new locks.
>>
>> Unless ktime_get is also a bad thing to do in a preempt disabled section?
>
> ktime_get() works fine in preempt_disable sections, although it may add
> some latencies, but you shouldn't need to worry about it.
>
> I like this solution the best too, but if it does go in, I would ask to
> send us the patch for adding the preempt_disable() and we can add the
> preempt_disable_rt() to it. Why make mainline have a little more
> overhead?
>
> -- Steve

Good! I will do that. Thanks for clarifying the irq and constraints on 
raw locks in the other thread.

-mario

> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>